Extracellular RNA (exRNA) is an emerging paradigm as endocrine signals in cellular communication, biomarker development, therapeutic applications and systemic physiology. This UH2/UH3 project is to test the hypothesis that salivary extracellular RNA (exRNA) can be developed for the clinical detection of human diseases. Our laboratory first reported the existence of a transcriptome and microRNA profile in cell free saliva followed by its scientific characterizations and clinical utilities including biomarker development for molecular oncology applications. Most recently we have performed RNA-sequencing in cell free saliva and reported three major types of RNA in saliva (mRNA, miRNA and snoRNA). This UH2/UH3 application is to test the hypothesis that salivary exRNA can be developed to detect gastric cancer by performing a biomarker development study to definitively validate salivary exRNA biomarkers for the detection of gastric cancer. We are selecting gastric cancer to be the human disease indication because of an ongoing productive collaboration with the Samsung Medical Center where we have already procured saliva from 500 gastric cancer patients and 2250 non-gastric cancer controls. This will permit the UH2 phase for exRNA biomarker discovery to begin immediately. Additional clinical samples will be procured in the UH3 phase, 375 cases and 375 non-gastric cancer match controls each year for two years. These clinical samples for discovery and validation will allow us to definitively validate if salivary exRNA can be used to detect gastrc cancer in a defined clinical setting (Context of Use). There are four Specific Aims in the UH2 phase of the project. Aim 1 is to randomly select saliva from 100 gastric cancer and 100 non-gastric cancer controls to be used in Aim 2 which is to perform comprehensive RNA-sequencing to comprehensively profile salivary exRNA to the nucleotide level. Aim 3 is to perform data and statistical analysis of the profiled salivary mRNA, miRNA, and snoRNA to select the top 20 salivary ex- mRNA, ex-miRNA and ex-snoRNA. Aim 4 is to verify the candidate exRNA biomarkers in the original discovery cohort. Only verified candidate salivary exRNA will be advanced to the UH3 phase. In the UH3 phase, Aim 5 is to enroll and procure saliva from an additional 750 gastric cancer patients and 750 non-gastric cancer controls. Aim 6 will use 500 of the gastric cancer saliva and 500 matched control subjects from Aim 4 to individually validate the verified candidate salivary exRNA biomarkers and configure a panel of validate exRNA biomarkers with highest performance using logistic regression analysis. The panel will be validated in Aim 7 using saliva from an independent cohort of 250 gastric cancer and 250 non-gastric cancer controls. The goals of this UH2/UH3 application are to demonstrate the clinical utility of salivary exRNA by the discovering and definitively validating salivary exRNA biomarkers for the detection of a human disease condition.